In recent years, much attention has been paid to ionic compounds that are liquid at room temperature (ionic liquids), which have high polarity, excellent dissolution performance for various materials, and the properties of being difficult to evaporate, having high ionic conductivity, and being chemically stable, etc. An ionic liquid is formed from a cationic component and an anionic component; in particular, since the cationic component is formed mainly from an organic material, there is the possibility of being able to create a large number of ionic compounds, and the application and development thereof has been anticipated in a wide range of fields such as electrolyte materials for various types of batteries, solvents for organic synthesis in the green chemistry field, solvents for separation and extraction, and organic conductive materials.
As one such ionic compound, an imidazolium compound has been reported. For example, JP, A, 3-34270 describes the use of 1-allyl-3-propylimidazolium chloride as an electrolytic solution of a secondary battery, and JP, A, 2002-145864 describes the use of 1-allyl-3-propylimidazolium iodide as an electrolyte of a wet solar battery. Furthermore, ‘Canadian Journal of Chemistry’, 1971, Vol. 49, pp. 325-332 describes 1-methyl-3-allylimidazolium bromide, 1,3-diallylimidazolium bromide, etc. However, with regard to a compound having an allyl group at the 1-position or 3-position of the imidazolium ring, no compounds other than those described in the above publications are known.
Among the ionic imidazolium compounds, there are those that are solid at room temperature, those that have high viscosity, those that have low ionic conductivity, etc., depending on the type of anionic group. These properties become a problem when the imidazolium compound is used as an electrolyte material for various types of batteries, a solvent for organic synthesis, a solvent for separation and extraction, etc. For example, there are the problems that it is necessary to dissolve those that are solid at room temperature in another organic solvent each time when they are used as a reaction solvent or an extraction solvent, it might be difficult to handle those that have high viscosity, particularly in the field of electrolytes, reaction solvents, etc., and those having low ionic conductivity cannot give satisfactory effects when they are used as a reaction solvent, an electrolyte, etc.
Because of this, for example, as an electrolyte or electrolytic solution for a lithium secondary battery, in order to enable its use under severe environments, there is a strong desire for it to be a liquid that has as low viscosity as an organic solvent at very low temperature (e.g. −40° C.), and as a solvent for an organic synthesis reaction there is a strong desire for it to be able to be used at very low temperature to high temperature (e.g. 250° C.) from the viewpoint of ease of handling and freedom in setting a reaction temperature.
Furthermore, compounds that are currently used as organic solvents have the serious problem that they badly affect the environment and animals and plants in terms of air pollution, water pollution, destruction of the ozone layer, etc. In particular, since the effect due to halogen-containing organic solvents is serious, regulations on their use, production, etc. have been tightened. There is therefore a desire for an organic solvent that has a performance that is the same as or higher than the above organic solvents but that does not affect the environment.